Mechanical telephone



(No Model.)

W. H. EASTMAN 8: D. J. ADAMS.

MECHANICAL TELEPHONE.

-No. 375,315. Patented Dec. 20, 1887.

WILLIAM H. EASTMAN AND DAVID PATENT OFFICE.

J. ADAMS, OF CONCORD, ASSIGNOBS, 9

BY MESNE ASSIGNMENTS, TO THE EUREKA TELEPHONE COMPANY,

OF NASHUA, NEW HAMPSHIRE.

MECHANICAL TELEPHONE.

SPECIFICATION forming part of Letters Patent No. 375,315, dated December20, 1887.

Application filed May 4, 1887.

To all whom it may concern:

Be it known that we, WILLIAM H. EAST- MAN and DAVID J. ADAMS, citizensof the United States, and residents of Concord, in the county ofMerrimac and State of New Hamppose set'forth, with thereceiving-diaphragm, I

of two conical diaphragms of thin sheet indiarubber, having their apexesin proximityito the center of the receiving diaphragm arranged nearlyparallel to each other, separated by an ai rchamber,and stretched over awooden ring surrounding the conducting-wire.

In the accompanying drawings a telephone is shown which embodies theprinciple of our invention, and Figure 1 is a back view of thistelephone, showing the back board removed. Fig. 2 is a front View of thetelephone. Fig. 3 is a sectional view.

In these several figures the same letters refer to the same parts.

We have represented our improved diaphragm and its attachment as usedwith a telephone-case of the box form; but they may be used with anyother form of telephone-case.

Referring to the drawings, A is the diaphragm attached at its edge to awooden frame, B, forming the front of the case and attached to a seriesof wooden posts. The sides of this case are formed of pieces of thinwood, 1), attached to these posts, and the back of the case is alsoformed of a piece of thin wood, E, se-

cured to the posts, and having a perforation in its center through whichthe conducting-wire passes. This manner of constructing the case formsno part of our invention, and it may be made in any manner by which achamber will be formed in the rear of the receiving-diaphragm. Thisdiaphragm is preferably dished, orof conical form, and is preferablymade of Serial No. 237,035. (No model.)

drum-head parchment. A sheet ofthin indiarubber is stretched over theoutside surface of the diaphragm, and is preferably made adherent to it.The effect of this rubber covering is to destroy the resonance of theparchment diaphragm, and thus prevent confusion of sounds and improvethe articulating-power of the telephone. not claim in thisspecification; but it may form the subject for another application for apatent.

F is the conducting-wire, attached to a button, G, at the center of thediaphragm and passing through the same. The button which we use ispreferably made of lead, and is sepaber, leather, or other similarsound-deadening material. Supported within the case about an inch fromthe receiviug-diaphragm,by wires ring, H, of less diameter than thereceivingdiaphragm, and c c are two nearly parallel diaphragms of thinsheet india rubber, which are stretched over this ring,- and areseparated from one another by an air-chamber. The rear one of these twodiaphragms has at its center a metallic disk, I, preferably of lead,through which the conducting'wire passes. This disk is brought almostinto cont-act with the back of the receiving-diaphragm A, after theproper tension has been given to the same, and is then suitably fixedupon the wire. In this way, and in addition, owing to the strain causedby the tension of the receiving-diaphragm A, the rubber diaphragms arecaused to assume a conical form and to be maintained in a tensecondition. The action of this device is to prevent the effect upon thereceiving-diaphragm A of the longitudinal and transverse vibrations ofthe conducting-wire due to its resonant property and to the effect ofwind, and thus prevent the roaring and ringing sounds which interferewith the perfect transmission of sounds by the molecular vibration ofthe conducting-wire, thereby enabling the instrument, as has been foundby experience, to transmit speech with distinctness for distances muchgreater than is usually possible with mechanical telephones.

Having thus described our invention, what This form of diaphragm we dorated from the diaphragm by a washer ofrubattached to the walls of thecase, is a wooden we claim, and desire to secure by Letters Pat- Inwitness whereof we have hereunto set our ent of the United States, is--hands in the presence f the two subscribing The combination,substantially as and for witnesses.

the purpose set forth, of the diaphragm A, the

5 c0nducting-wire F, the button G, the disk I, WILLIAM H. EASTMAN.

the ring H, supported within the telephone- DAVID J. ADAMS. case, andthe conical tense diaphragrns of thin sheet-rubber c a, stretched oversaid ring and NVitnesses: separated from each other by an air-space,sub- ALEX. L. HAYES, IO stantially as and for the purpose set forth. J.E. MANNING.

